From 6ad0aca7e0609c91cf91868b9081a3cdd2652016 Mon Sep 17 00:00:00 2001
From: Recep Aslantas <info@recp.me>
Date: Fri, 22 Mar 2024 21:59:10 +0300
Subject: [PATCH] fix refract

---
 include/cglm/vec2.h | 6 +++---
 include/cglm/vec3.h | 6 +++---
 include/cglm/vec4.h | 6 +++---
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/cglm/vec2.h b/include/cglm/vec2.h
index 4eaca3d..58878f5 100644
--- a/include/cglm/vec2.h
+++ b/include/cglm/vec2.h
@@ -746,15 +746,15 @@ glm_vec2_refract(vec2 I, vec2 N, float eta, vec2 dest) {
 
   ndi = glm_vec2_dot(N, I);
   eni = eta * ndi;
-  k   = eta * eta + eni * eni;
+  k   = 1.0f + eta * eta - eni * eni;
 
-  if (k > 1.0f) {
+  if (k < 0.0f) {
     glm_vec2_zero(dest);
     return;
   }
 
   glm_vec2_scale(I, eta, dest);
-  glm_vec2_mulsubs(N, eni + sqrtf(1.0f - k), dest);
+  glm_vec2_mulsubs(N, eni + sqrtf(k), dest);
 }
 
 #endif /* cglm_vec2_h */
diff --git a/include/cglm/vec3.h b/include/cglm/vec3.h
index 49a5b29..1fdd483 100644
--- a/include/cglm/vec3.h
+++ b/include/cglm/vec3.h
@@ -1260,15 +1260,15 @@ glm_vec3_refract(vec3 I, vec3 N, float eta, vec3 dest) {
 
   ndi = glm_vec3_dot(N, I);
   eni = eta * ndi;
-  k   = eta * eta + eni * eni;
+  k   = 1.0f + eta * eta - eni * eni;
 
-  if (k > 1.0f) {
+  if (k < 0.0f) {
     glm_vec3_zero(dest);
     return;
   }
 
   glm_vec3_scale(I, eta, dest);
-  glm_vec3_mulsubs(N, eni + sqrtf(1.0f - k), dest);
+  glm_vec3_mulsubs(N, eni + sqrtf(k), dest);
 }
 
 #endif /* cglm_vec3_h */
diff --git a/include/cglm/vec4.h b/include/cglm/vec4.h
index 212a872..d8c2ea0 100644
--- a/include/cglm/vec4.h
+++ b/include/cglm/vec4.h
@@ -1347,15 +1347,15 @@ glm_vec4_refract(vec4 I, vec4 N, float eta, vec4 dest) {
 
   ndi = glm_vec4_dot(N, I);
   eni = eta * ndi;
-  k   = eta * eta + eni * eni - 1.0f;
+  k   = 1.0f + eta * eta - eni * eni;
 
-  if (k > 0.0f) {
+  if (k < 0.0f) {
     glm_vec4_zero(dest);
     return;
   }
 
   glm_vec4_scale(I, eta, dest);
-  glm_vec4_mulsubs(N, eni + sqrtf(1.0f - k), dest);
+  glm_vec4_mulsubs(N, eni + sqrtf(k), dest);
 }
 
 #endif /* cglm_vec4_h */